Flowing multiphase effluents in a single pipe is of high industrial importance since it allows effluent conveyance installations to be simplified by using a minimum number of pipes and investments to be minimized. The problem posed during the conveyance of multiphase fluids is due to the presence of a gas phase and of a liquid phase which display a different behaviour when pressure is communicated thereto.
Many methods are currently used for the transportation of such fluids.
The most simple method consists in separating the two phases and in raising their pressure separately before transferring them into different pipes. This method entails relatively high production costs.
The devices and methods described in patents FR-2,424,472 and FR-2,424,473 filed by the applicant allow the constituents of a two-phase fluid to be conveyed in a single pipe. These patents teach to dissolve the near total of free gas in the liquid in order to obtain a fluid only made up of liquid, so that it may be processed by the pumping means. This leads to very high costs since the gas phase has to be entirely dissolved.
Another procedure consists in using pumps designed for communicating to the multiphase fluids a pressure value providing their transfer over a certain distance. However, most of these pumps, if not all of them, are adapted for transferring effluents having a GLR value contained in a definite interval. To remedy this limitation, devices are used for controlling the effluents located upstream from the pump, which allow an effluent whose GLR value is compatible with the working characteristics of the pump to be delivered thereto. The GLR ratio is defined as the ratio of the gas phase to the liquid phase (Gas/Liquid Ratio).
However, devices of this type have working limitations, notably when the GLR ratio variations are too sudden, for example when too great an amount of gas with respect to the processing capacity of the pump reaches the pump inlet, this amount of gas being called a "gas pocket".
Within the scope of the current development of multiphase fluid transportation, it is increasingly important to have a method and a device allowing multiphase fluids to be transferred in a single pipe, whatever the value and the variation with time of their GLR ratio when leaving the well.
The composition of such an effluent may for example have successively the form of a gas pocket, of liquid plugs (GLR=0), or of an effluent whose (gaseous phase)/(liquid phase) ratio value GLR ranges between zero and a value corresponding to a gas pocket for example.